It is known in the prior art to couple a pointing device (e.g., a mouse or a trackball) to a keyboard in a computer system. For example, U.S. Pat. No. 5,305,449 to Ulenas (“the Ulenas '449 patent”) discloses the combination of a keyboard 18, a pointing device 22 (i.e., a mouse or a trackball) and an adapter electronics circuit 32 which converts signals from a pointing device 22 into the cursor key codes of a keyboard 18. As is well-known in the art, when a key on the keyboard 18 is depressed, a switch closes, and encoder electronics of the keyboard 18 converts the switch closure into a key code and then transmits the key code to the host computer. The Ulenas '449 patent discloses extending the keyboard's encoder electronics to accept the signals from the pointing device 22 and to convert these signals into the corresponding cursor key codes of the keyboard 18 using the adapter electronics 32 incorporated therein. The Ulenas '449 patent discloses in FIG. 5 and the corresponding text incorporating the adapter electronics 32 into the keyboard 18, so that the pointing device 22 is coupled to the keyboard 18. The adapter electronics 32 converts the signals from the pointing device 22 into keyboard signals and passes the key codes from the keyboard 18 to the host computer. The encoder electronics 32 does not perform other functions, such as scanning the keyboard 18 or the pointing device 22 for data or formatting such data for subsequent transmission.
The combination disclosed in the Ulenas '449 patent effectively disguises the pointing device 22 to appear as the keyboard 18, and thus the combination is not suitable for use in a computer system that uses the Universal Serial Bus (“USB”) Specification, which separately identifies each peripheral device according to a Human Interface Device (“HID”) protocol. Indeed, the combination disclosed in the Ulenas '449 patent cannot operate in a USB environment. This is a significant drawback, since virtually all new personal computer systems include one or more USB ports, and the use of exclusively USB ports in computer systems is expected to dominate the interfacing of personal computer peripherals in the years to come. The USB Specification permits the personal computer to communicate with numerous peripheral devices through a single jack while always recognizing that each device is a separate device. No device need be disguised to appear as another device.
U.S. Pat. No. 5,831,597 to West et al. (“the West '597 patent”) discloses in FIG. 9 the combination of a keyboard 366, a touch input device 372, and a mouse device 376 that are connected to a processor 362 by a Universal Serial Bus. A cable 378 provides a direct connection between the USB port 370 of the processor 362 and the keyboard 366. A cable 380 provides an extension of the USB between the keyboard 366 and the input device 372. A still further extension of the USB is a cable 375 which is connected to the mouse device 376. In the combination disclosed in FIG. 9 of the West '597 patent, the keyboard 366 must include a USB hub device. In accordance with the USB Specification, the USB hub device includes a hub controller which provides status, data, control functions for the Universal Serial Bus, and permits a USB host to access the hub device at upstream ports as well as at downstream ports on the Universal Serial Bus. Furthermore, in order for the mouse device 376 to be connected in series with the keyboard 366 and the input device 372 on the USB, the mouse device 376 must be “intelligent,” i.e., the mouse device 376 must include its own microcontroller.
The West '597 patent illustrates the type of interfacing of peripheral devices that is contemplated by the USB Specification, i.e., a host computer 362 with a peripheral device (keyboard 366) that is a function/hub that includes within the peripheral device a USB hub device, a second peripheral device (touch input device 372) that is a second-tier function/hub device that includes within the peripheral device another USB hub device, and a function (mouse device 376) that includes a microcontroller. The USB hub devices that are included within the peripheral devices require connected functions to have their own microcontrollers. These hub devices facilitate the addition of more USB functions than may be practically needed.
As subsequent revisions of the USB Specification moves toward increased bit rates, USB ports will increase in cost. In Version 1.1 of the USB Specification, USB ports can be high speed (12.0 Mbits per second) or low speed (1.5 Mbits per second). The proposed Version 2.0 of the USB Specification sets forth bit rates of up to 240 to 480 Mbits per second. With respect to a USB-compatible computer keyboard, which typically includes a USB hub with two USB ports, a commercially significant consequence of an increase in the USB bit rate is the increased cost involved in integrating higher-speed USB ports into the keyboard. This is due primarily to the ancillary electronics that are necessary to support the higher-speed USB ports, particularly the filtering that is needed to ensure that the keyboard complies with various electromagnetic compatibility (EMC) requirements, which may be imposed by any of a number of sources including, for example, the U.S. Federal Communications Commission. As a general matter, then, the higher the speed of a USB port, the more expensive it is to integrate the USB port into a keyboard.
The trend, as evinced by the proposed Version 2.0 of the USB Specification, is toward higher USB bit rates. Keyboards that integrate therein the USB ports that will be required to support the higher bit rates will undoubtedly become more expensive, for the reasons detailed above. Consequently, there is a need in the art for a cost-effective input device that can be used in computers systems that are designed to operate in a high bit rate USB environment.